Recognizing the relative effects of environmental versus human factors to understand the conservation of coastal dunes areas

Coastal dunes are extremely complex sandy habitats and a place with considerable exchanges of mass and energy which support valuable biodiversity. During the last century, anthropogenic impact on coastal dunes has increased around the Mediterranean area leading to a decline of these ecosystems. However, it is not clear whether the status of a coastal dune system is more closely linked to the environmental dynamism or to the effects of the anthropogenic pressure. To explore this issue, the pocket-beach of Sa Mesa Longa (Sardinia), including two areas subjected to a different level of environmental and human pressures was selected as a study area. A total of 43 plots were randomly placed along nine transects orthogonal to the coastline; in each plot the presence and coverage of all vascular plants were measured to calculate a set of indices (i.e., Diversity index: Hdune; Evenness: E; Natural diversity index N; Endemicity index: EI) elaborated for the coastal dune systems. Our results indicate a high degree of conservation for Sa Mesa Longa beach; both the diversity (Hdune) and Endemicity (EI) indices mean values increased moving away from the shoreline to inland with a similar trend in the two areas. Human-related factors did not seem significantly to influence the conservation status of a dune system; a clear effect of the factors linked to the natural dynamism of such environments seemed not even evident if the floristic diversity is analyzed. Although on a small scale human trampling does not seem to be able to have a significant impact, the conservation status of a Mediterranean coastal dunes seems instead to be linked to a complex interaction of the two categories of factors. However, further studies will be necessary to understand the effects of touristic activities on coastal dunes as key to planning management strategies for these fragile ecosystems.